Low heat build-up capstock system and extrusion technology for solid and foamed profiles in dark colors

ABSTRACT

A weatherable, low heat build-up capstock system comprising an acrylic cap, a pigment system that is IR transparent to a greater degree than existing pigment systems, an IR reflective substrate, and an extrusion system for same.

PRIORITY

This application claims priority of the filing date of co-pending U.S.Provisional Patent Application No. 60/632,754.

TECHNICAL FIELD

The invention concerns extruded plastic profiles with a low heatbuild-up, weatherable capstock and the method and apparatus forextruding such products in hollow or foamed vinyl profile.

BACKGROUND OF THE INVENTION

Milled wood products have formed the foundation for the fenestration,decking, venetian blinds, shutters, decking and remodeling industriesfor many years. Historically, ponderosa pine, fir, red wood, cedar andother coniferous varieties of soft woods have been employed with respectto the manufacture of residential window frames, residential siding,outer decking and exterior shutters as well as interior venetian blindsand shutters. Wood products of this type inherently possess theadvantageous characteristics of high flexural modulus, good screwretention, easy workability (e.g., milling, cutting), easy paintability,and for many years, low cost. Conversely, wood products of this typehave also suffered from poor weatherability in harsh climates potentialinsect infestation such as by termites, and high thermal conductivity.In addition, virgin wood resources have become scarce causingcorrespondingly high material costs.

In response to the above described disadvantages of milled woodproducts, the fenestration industry, in particular, adopted polyvinylchloride (PVC) as a raw material. Hollow, lineal extrusions manufacturedinto window frames became an enormous success, particularly at the lowerend of the price spectrum. The window frames made from hollow PVClineals (often referred to as “vinyl windows”) have exhibited superiorthermal conductivity, water absorption resistance, rot and insectresistance compared to painted ponderosa pine. Although such extrusionsfurther enjoyed a significant cost advantage over comparable milled woodproducts, these PVC products had a significantly lower flexural modulusand higher coefficient of thermal expansion and were difficult to painteffectively. Similarly, hollow PVC lineals have replaced wood forVenetian blind and shutter frames, slats and related components havinglargely the same advantages and disadvantages as PVC window extrusions.Also, foamed polymer solid extrusions have been used to replace woodwindow frames and sashes, Venetian blind and shutter frames and slats.The foamed polymer extrusions may contain organic or inorganic fillers,such as wood flour and talc, respectively, where advantageous forimproved physical properties such as stiffness and/or to reduce the costof the extrusions.

As noted above, windows manufactured with wooden frames and sashes caneasily be stained or painted virtually any color. Thus, the color of thewindow frame and sash could be chosen to accent or contrast with thecolor of the exterior of the house. The PVC products are typicallyavailable only in white or beige. Understandably, window and doorprofiles in dark colors, such as “Hunter Green” and “Bronze,” have longbeen demanded in the industry. Still, there is the significant issue ofheat build-up, which largely accounts for the relative lack of darkcolors in PVC windows and other products formed of extruded plasticlineals.

When referring to dark colors herein, the inventor is referringgenerally to colors with an Lh value between 13 and 40. For example, perASTM 4726-02, dark brown is defined as a color with an Lh between 13 and33, an ah between −1.0 and 6.0 and a bh between 1.0 and 6.5. Per AAMA308-02, dark green is defined as a color with an Lh between 20 and 40,and ah between −20 and −2 and a bh between −2.0 and 4.0. The inventordefines the color red to have Lh values between 20 and 30, ah valuesbetween 13 and 23, and bh values between 6 and 12.

For example, it is well known in the vinyl window industry that PVCwindow frames will fail in unacceptably high numbers, exhibitingsymptoms such as buckling, warping and sagging, if the window framesbecome too hot. The environmental factors typically causing a windowframe to warm is a high ambient air temperature in addition to visiblelight and near infrared solar radiation. It can be shown that ASTMD4803, Predicted Heat Build-Up, is a good predictor of productperformance related to heat induced PVC window failure. That is, it isknown to the inventor what products have failed in the field, whatproducts have not failed in the field, and what the ASTM D4803 predictedheat build-up values are for those products. It is known that the nearinfrared portion of solar radiation is a significant portion of theenergy radiated from the sun and the properties of a pigment systemrelated to this spectrum will effect what is known as the heat build-upof that pigment system.

In order to color an extrusion or a capstock resin for application on anextrusion, various pigments are combined, typically by a color house,within a base resin where individual pigments absorb or reflect certainportions of the visible light spectrum causing the base resin to appearto be a certain predetermined color. Still, pigment systems that are thesame color may have substantially different heat build-upcharacteristics as the near infrared portion of solar radiation is asignificant portion of the energy radiated from the sun and the nearinfrared portion of solar radiation is invisible to the human eye.

In general, the art of coatings, capstocks, laminates, and mono-colorextrusion has been concerned with using highly IR reflective pigmentsystems. Even state-of-the-art IR reflective pigment systems still limitthe useful color spectrum to lighter shades, and darker colors usingsuch state of the art pigment systems will lead to excessive heatbuild-up and, ultimately, product failure in the field. Thus, there is aneed for dark colors that will not build up excessive heat and thereforefail at the point of use.

Applying a thin capstock layer to hollow vinyl profile and solid foamedpolymer resin extrusion is well known in the art. Typically, thecapstock layer is applied for the purpose of achieving color,weatherability, and certain appearance attributes in a cost-effectivemanner. Frequently, this allows the practitioner to use a lower-costmaterial in the substrate and therefore reduces total product cost.However, the useful color spectrum that can be applied to PVC hollow orfoamed profile extrusion is limited to colors and pigment systems thatdo not build up excessive heat and thereby cause the body of the productto distort.

Other means to apply a layer of color to hollow vinyl profile and foamedvinyl extrusion include coatings and laminates. In general, bothprocesses require a secondary operation after the hollow or foamedprofile is extruded, and both processes are also limited in useful colorspectrum due to heat build-up constraints. In addition, coating andlaminate application typically requires the use of hazardous materialsand is subject to various safety and environmental regulations. Coatingsin particular are easily damaged during fabrication and installation andextensive touch-up is often required after the finished window or doorunit is installed.

Last, mono-color extrusions are also common in the art. As withcapstocks, coatings, and laminates, the useful color spectrum is limitedto colors that do not readily absorb in the IR spectrum and therefore donot build up sufficient heat to distort the body of the extrusion.Typically, mono-color extrusions are seen in lighter shades and pastelswhere heat build-up is not a problem and where the required amount ofpigments does not unduly increase the cost of the extrusion.

Thus, heretofore, dark colors such as Hunter Green and Bronze have beenachieved only by using special coatings and laminates, and even thenthere are a limited number of suppliers of coatings and laminates thatare suitable for exposure in demanding environments, such as Arizona,Nevada, and Southern California.

SUMMARY OF THE INVENTION

It is therefore an object of the invention to provide a heat build-upresistant extrudate with a dark-colored capstock which comprises an IRreflective substrate portion formed of a first thermoplastic resin thatis substantially reflective of solar infrared radiation and adark-colored capstock portion that is formed of a second thermoplasticresin that is significantly transmissive of solar infrared radiation andthat covers at least a portion of the reflective substrate.

It is a further object of the invention to provide a method of producinga low heat build-up extrudate with a dark-colored capstock thatcomprises feeding of an IR reflective substrate formed of a firstthermoplastic resin that is substantially reflective of solar infraredradiation into a first extruder, feeding a dark-colored capstock that isformed of a second thermoplastic resin that is significantlytransmissive of solar infrared radiation into a second extruder andoutputting the first and second extruders to an extrusion die that formsthe extrudate into a predetermined shape where the dark-colored capstockcovers at least a portion of the IR reflective substrate.

It is a still further object of the invention to provide for anextrusion line for the production of a low heat build-up extrudate witha dark-colored capstock which comprises a first extruder for extruding afirst thermoplastic resin that is substantially reflective of solarinfrared radiation, a second extruder for extruding a secondthermoplastic resin that is significantly transmissive of solar infraredradiation, an extrusion die operatively coupled to the outputs of thefirst and second extruders wherein the extrusion die has upstream anddownstream ends and forms the extrudate into a final extrudate of apredetermined profile at the downstream end that wherein the extrudatecomprises an IR reflective substrate portion that covers at least aportion of the extrudate and that is formed of the first thermoplasticresin, and a dark-colored capstock portion that is formed of the secondthermoplastic resin that covers at least a portion of the reflectivesubstrate.

In a preferred embodiment of the inventive low heat build-up extrudatewith a dark-colored capstock, the extrudate comprises an IR reflectivesubstrate portion formed of a first thermoplastic resin that issubstantially reflective of solar infrared radiation containing greaterthan about 8 parts titanium dioxide (TiO₂) per hundred parts base resin,a dark-colored capstock portion that is formed of a second thermoplasticresin that is less than about 30 thousandths of an inch thick and mostpreferably between 4 thousandths and about 8 thousandths of an inchthick, that is significantly transmissive of solar infrared radiation,and that covers at least a portion of the reflective substrate.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of an extrusion line of a type used with theinventive method.

FIG. 2 is an exploded view of the upstream side of a multi-plateextrusion die for use in a preferred embodiment of the inventive methodand with a preferred embodiment of the inventive extrusion line.

FIG. 3 is an exploded view of the downstream side of a multi-plateextrusion die for use in a preferred embodiment of the inventive methodand with a preferred embodiment of the inventive extrusion line.

FIG. 4 is a view of a preferred embodiment of the inventive product andof the flow of thermoplastic materials through the multi-plate extrusiondie of FIGS. 2 and 3.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The inventor and persons of ordinary skill in the art of extrudingplastics for the fenestration industry understand that ASTM D 4803,Predicted Heat Build-Up, ASTM Standard Test Method for Predicting HeatBuildup in PVC Building Products (1997), is a good predictor of productperformance as it relates to thermal failures due to excessivetemperatures within a structural extrusion from absorbing solarradiation primarily in the near-infrared spectrum (NIR). That is, it isknown to the inventor what products have failed in the field, whatproducts have not failed in the field, and what the ASTM D4803 predictedheat build-up (PHBU) values are for those products. ASTM D4803 gives apredicted heat build-up in degrees Fahrenheit above ambient, e.g., aPHBU of 50° F. would indicate a test specimen temperature that is 50° F.greater than test ambient air temperature. Usefully, it is possible totailor an IR transparent color capstock system and IR reflectivesubstrate for predicted heat build-up values that are either known orpredicted to have acceptable performance in the field. The inventor isaware of significant numbers of heat build-up related failures ofstructural PVC fenestration components in use in the continental UnitedStates where the horizontal PHBU values were 59° F. and believes that ahorizontal PHBU of 56° F. or less for a production PVC structuralfenestration product would appropriately limit the likelihood of suchfailures. A PHBU of 56° F. or less may be appropriate for temperateregions not subject to high solar radiation. For products other thanfenestration products, such as Venetian blinds and shutters, or wherethe base resin is more or less tolerant of increased temperatures, theacceptable heat build-up values could be increased or decreased forreasons well understood in the plastics extrusion industry in a mannerfurther described hereinbelow. As is well understood by one of ordinaryskill in the plastics extrusion arts, the heat resistance of a productcan be increased by changes made to the base resin such as by the use ofa heat resistant PVC. These prior art solutions can be used incombination with the present invention to allow a useable fenestrationproduct where the horizontal PBHU values are higher than the valuesrecommended above.

It should be understood that further reduction of the PBHU will decreasethe likelihood of heat build-up related failures. Still, excessiveresistance to heat build-up is of no value to an end user in that theonly goal is to ensure that the fenestration product or other extrudedproduct does not warp, buckle or sag in use. Therefore, cost increasesentailed in lowering the PHBU value or by increasing the heat resistanceof the base extrusion must be justified as significantly lessening thelikelihood of product failure.

The present invention utilizes a dark colored capstock for color that issignificantly NIR transparent rather than NIR reflective, and relies onan NIR reflective substrate for the NIR reflectance. In effect, thismeans at least a two-component system is necessary to impart both thecolor and low heat build-up properties. For extrusion of a preferredembodiment of the invention, namely a capstocked, hollow, thin-walledpolyvinyl chloride resin based extrusion, two extruders are required, asin a typical capstocking operation long found in the prior art, where aprimary extruder extrudes a hollow, thin-walled extrusion, preferablyformed of PVC resin, and a secondary capstocking extruder extrudesdark-colored capstock over at least a portion of the surface of the baseextrusion. Salient differences from the prior art is that this PVCsubstrate must be tailored for near infrared solar (NIR) reflectance andthe dark-colored capstock must be substantially transmissive of NIR asis more thoroughly discussed below. Another preferred embodiment of theinvention comprises a foamed Styrene-Acrylonitrile Copolymer (SAN) basedwood composite base extruded by a base extruder or a foamed PVC basedbase extruded by the base extruder, an NIR reflective substrate layerformed by a first capstocking extruder, and a dark-colored capstock thatis significantly transmissive of solar infrared radiation (NIR) isformed by a second capstocking extruder. A further embodiment wouldprovide comprises a primary extruder that extrudes a hollow, thin-walledextrusion, preferably formed of PVC resin and not necessarily NIRreflective, an NIR reflective substrate layer formed by a firstcapstocking extruder, and a dark-colored capstock that is significantlytransmissive of solar infrared radiation (NIR) is formed by a secondcapstocking extruder.

In addition to the various extruders discussed above, appropriatecalibrators, pullers and saws are needed for the production of the abovedescribed inventive extrusions Additionally, stresses imparted duringthe extrusion calibration process will affect the apparent color of thepigment systems of the preferred embodiments. Thus, the presentinvention also embodies a means to eliminate those stresses, andtherefore provide a consistent visual color, by applying heat after theproduct exits the extruder calibrator.

Tailoring the heat build-up performance of an extrusion is conducted byessentially three means. First, the thickness of the dark-coloredcapstock is manipulated to minimize IR absorbance as NIR initiallypasses through the dark-colored capstock and as it is reflected off ofthe substrate back through the dark-colored capstock. This manipulationmust also be done in a manner that preserves the visual color of thecapstock. Second, the substrate is manipulated to provide the requisiteIR reflectance, most commonly by manipulating the loading of TiO2 butalso with consideration of other substrate constituents. Third, thepigments in the dark-colored capstock required to impart particularcolors should be optimized to minimize their absorbance of NIR. Inpractice, all three means must be optimized for a particularcapstock/color/substrate combination to yield a functional finalproduct.

A preferred and useful pigment and cap material combination for the darkcolored capstock material is available from Lanier Color Company and canbe shown to posses the IR and weatherability properties desired, namelythat the pigment system is substantially transmissive of NIR and such apigment system is used in the inventive examples discussed, hereinbelow.The body of the dark colored capstock is Kaneka Corporation'sproprietary XM20, which is an extrusion grade acrylic. This acrylic hasa melt index value between approximately 13 g/10 min. and 20 g/10 min.as tested using ASTM D1238 standard at 230° C. and 3.8 kg mass. Thisuseful Lanier pigment system uses a black base pigment that provides asuitable base to which other pigments can be added to achieve a desiredparticular color or chroma (e.g., forest green or bronze) as is wellunderstood by color houses and those of ordinary skill in the art.Individual pigments may be reflective or transmissive of NIR so long as,overall, the pigment system is substantially NIR transmissive. Thepreferred Lanier pigment system, or a substitute that is substantiallyNIR transparent, would be suitable for use in the present invention andwould achieve the ends of the present invention. The dark coloredcapstock may be solid colors or may be formed into wood grains or otherfinishes with textured appearances. Further, touch-up paints that aresubstantially NIR transparent based on similar NIR transmissive pigmentsystems may be used to repair minor scratches or gaps in the darkcolored capstock such as may occur at the corner welds in a windowframe.

Suitable IR reflective substrates are available from various sources ormay be custom blended depending on IR reflectivity requirements buttypically can comprise a white outdoor suitable polymer such asextrusions suitable for exterior use in a high solar exposureenvironment. A preferred IR reflective substrate is bright white hollowPVC window lineals containing 9 parts TiO₂ per 100 parts base PVC resin(9 phr TiO₂) further including various additives, modifiers and processaids as is well understood in the art. The inventor believe that linealscurrently used in residential window frames would likely be a suitablesubstrate for this invention although the substrate NIR reflectiveproperties may be adjusted as further described hereinbelow. Further,various pastel PVC lineals, in such shades as almond and adobe, and PVCwood-grain colored lineals may be useful so long as the lineals are IRreflective.

A preferred embodiment of base extrudate to be coated with a NIRreflective capstock and then the dark colored capstock would comprise afoamed Styrene-Acrylonitrile Copolymer (SAN) based wood composite suchas the formulation described in U.S. application Ser. No. 09/452,906,entitled “Wood Fiber Polymer Composite Extrusion and Method” where theamount of wood flour is reduced to approximately 2% wood flour by weightin the formulation. Alternatively, the wood flour can be replaced with200-mesh talc powder with favorable results. Another preferredembodiment of the base extrudate would be a foamed PVC (with variousadditives, modifiers, process aids and blowing agents) base extruded bythe base extruder. A further base extrudate would be a hollow PVC linealthat does not contain significant amounts of TiO₂ to reduce the baseextrudate cost. A preferred IR reflective capstock would be a brightwhite PVC capstock with 10 phr TiO₂. Further, capstocks of variouspolymers in white and in various pastel colors, such as almond andadobe, or wood-grain colored capstocks may be used so long as thecapstock is IR reflective. TABLE 1 Specimen Cap % TransmittanceDescription Thickness UV VIS NIR Solar Inventive Dark Cap 1 0.009″ 0.02.1 42.4 21.6 Inventive Dark Cap 2 0.028″ 0.0 0.7 25.8 12.9 Prior ArtDark Cap 1 0.007″ 0.0 0.0 4.4 2.2 Prior Art Dark Cap 2 0.023″ 0.0 0.00.2 0.1The difference between the process and extrusions disclosed herein andthe prior art are aptly illustrated by the data of Table 1. Table 1shows the results of testing performed in accordance with ASTM StandardTest Method E903 (1996) for Inventive Dark Caps 1 and 2 including thesubstantially NIR transmissive dark-colored capstock to be used with theinventive process and product of this patent application. Prior Art DarkCaps 1 and 2 show a representative prior art commercially availabledark-colored capstock and were subject to the same tests. As can bereadily seen, Inventive Dark Caps 1 and 2 allow 42.4% and 25.8%,respectively, of NIR to pass through them in this test. In contrast,Prior Art Dark Caps 1 and 2 allow only 4.4% and 0.2% to pass through.This test data illustrates the prior art approach to dark-coloredcapstocks; reflectance of NIR by dark color capstock was attempted andonly 4.4% of NIR is not absorbed or reflected by the 0.007″ thickspecimen. In contrast, the Inventive Dark Caps 1 is 0.009″ thick andneither absorbs nor reflects 42.4% of NIR but instead allows it to passthrough. This invention provides for a highly NIR reflective substrateto deal with this NIR which passes through dark-colored capstock.

This data further illustrates another important concept to practicingthis invention, namely the correlation between capstock thickness andthe amount of NIR transmittance. Please note that a 0.009″ thick sampletransmits 42.4% of NIR while a 0.028″ thick sample transmits only 25.8%.Since reflectance is dominated by the surface of the dark-coloredcapstock essentially meaning that the 42.4%-25.8%=16.6% of NIR that isnot transmitted by the thicker 0.028″ sample is absorbed by thedark-colored capstock causing increased heat build-up for thickerdark-colored capstocked extrusion of the present invention. Thisillustrates the importance of the first means for limiting heat build-upin the inventive process; namely the decreasing of the thickness of thedark-colored capstock to minimize NIR absorbance as NIR initially passesthrough the dark-colored capstock and as it is reflected off of thesubstrate back through the dark-colored capstock. TABLE 2 WhiteSubstrate Cap Percent Percent Samples Pressed on TiO₂ Loading ThicknessNIR Solar White Substrate (PHR) (in.) Reflectance Reflectance InventiveDark Cap 3 10 0.011 74.8 43.7 (10 phr TiO₂ substrate) Inventive Dark Cap4 12 0.009 76.8 44.7 (12 phr TiO₂ substrate) Inventive Dark Cap 5 140.010 77.1 44.8 (14 phr TiO₂ substrate) Prior Art Dark Cap 3 10 0.00832.9 19.9 (10 phr TiO₂ substrate) Prior Art Dark Cap 4 12 0.009 35.519.6 (12 phr TiO₂ substrate) Prior Art Dark Cap 5 14 0.009 32.6 19.7 (14phr TiO₂ substrate)

Table 2 shows data from embodiments of the present invention, InventiveDark Cap 3, 4 and 5, compared to prior art products, Prior Art Dark Cap3, 4 and 5, where the dark capstocks are of similar colors and arepressed onto white substrates having differing titanium dioxide (TiO₂)levels. Percent NIR reflectance was determined for the dark colored capportions of each of the examples in Table 2. Table 2 illustrates thesecond consideration, namely that the substrate is manipulated toprovide the requisite NIR reflectance and most commonly increased ordecreased by manipulating the loading of TiO₂ with consideration ofother substrate constituents. It should be noted that, as the TiO₂ levelof the substrate in the inventive examples is increased, the percent NIRreflectance also increases. The TiO₂ level of Inventive Dark Cap 3 is 10parts per hundred resin and the percent NIR reflectance is 74.8 percent.In Inventive Dark Cap 4 where the TiO₂ level is 12 parts per hundredresin the percent NIR reflectance is 76.8 percent. Further, InventiveDark Cap 5, where the TiO₂ level is 14 parts per hundred resin, thepercent NIR reflectance is 77.1 percent. Thus, by increasing the NIRreflectance of the substrate by increasing the TiO₂ level one canincrease the percent NIR reflectance of an extrusion with the inventivedark colored capstock.

In contrast, the exemplary prior art, Prior Art Dark Cap 3, 4 and 5, donot appear to be effected in a significant way by the TiO₂ level as thePrior Art Cap 3, with 10 parts per hundred resin, and the Prior Art Cap5, with 14 parts per hundred resin, have very similar percent NIRreflectance. One would not expect that the prior art dark cap would beaffected by the NIR reflectance of the substrate as essentially all ofthe NIR is either reflected or absorbed by the prior art dark coloredcap.

FIG. 1 illustrates an extrusion line 10 suitable for practicing theinventive process. An extrusion line suitable for use in an embodimentof the inventive process is disclosed in The extrusion line 10 consistsof at least two extruders including primary extruder 20 that includes afeed hopper 12 that drops into a feed column 14 which further connectsto a pre-mixer 16. Port 18 also feeds into feed column 14 for theaddition of micro ingredients such as a blowing agent. Alternatively,such micro ingredients can be added at hopper 19 directly into thepremixer 16. The ingredients that reach Premixer 16 are fed directlyinto the mouth of primary extruder 20. A dark colored capstock extruderand, in a preferred embodiment, a substrate capstock extruder, havingessentially these same features as described above for the primaryextruder is further disclosed.

A multi-plate extrusion die 22 is further described below with referenceFIG. 2, but multi-plate extrusion die 22 is operatively attached to theprimary extruder 20 the output of the primary extruder 20. The extrusionis shown at reference numeral 24 after it has exited multi-plateextrusion die 22. Extrusion 24 then enters calibrator 26 which is of theordinary type used in plastic profile extrusion and which includes sizerplates which form extrusion 24 into its final form and spray nozzles tocool and solidify extrusion 24.

After extrusion 24 exits calibrator 26, it enters heat treatment tube28. Heat treatment tube 28 has formed of PVC pipe approximately threefeet long and of a diameter to allow easy clearance for extrusion 24 topass through it. Preferably, at the entrance and exits of heat treatmenttube 28, leister heaters 30 blow hot air into the tube and overextrusion 24. Alternatively, the heat treatment tube 28 can also beserved by an IR heating tube to heat the exterior surface of extrusion24. Further, the leister heaters 30 could be replaced with heat guns, IRheaters, radiant heaters or other devices that would heat the interiorof the heat treatment tube 28 and thereby heat the surface of extrusion24. The heat treatment tube 28 could be replaced with just liesterheaters 30 or their substitutes that were noted above should bow ofextrusion 24 not be a significant concern. Extrusion 24 then continueson to puller 32 and saw 34 that are entirely conventional extrusionequipment long in use in the art.

The purpose for the heat treatment tube is to eliminate the occurrenceof “streaking” in the color cap where upon inspection, there will bestreak of a differing shade in a line traveling down the length ofextrusion 24 and it should be understood that heat treatment tube 28 orits substitutes would not be needed should there be no color streaking.The inventor believes that this streaking is caused by stresses formedin the surface of the dark colored capstock by the calibration andcooling process which of necessity causes the surface of the darkcolored cap to contact the interior surface of calibrator 26 and causesthe part to cool most quickly on the surface and, more gradually, forthe interior portions of the extrusion to cool relatively more slowly.This streaking most typically is of a red shade. The inventor has foundthat this streaking can be easily removed by heat treatment of thesurface of dark colored capstock. Inventor has further found that use ofthe heat treatment tube, as described above, heats the entire surface ofextrusion 24 thus avoiding causing extrusion 24 to bend or bow as can becaused by heating only one side of the extrusion such as by directlyblowing hot air onto a surface of extrusion 24. Inventor has found thatheating the surface of extrusion 24 to approximately 145° F. to 150° F.will remove the color streaking observed in the dark colored capdisclosed herein and has found that Leister heaters 30 blowing air atapproximately 225° F. into the tube has raised the surface of examplesof extrusion 24 to the desired 145° F. to 150° F.

FIG. 2 is an exploded view of the upstream sides of the individualplates of the multi-plate extrusion die 22 for use in a preferredembodiment with a foamed primary extrudate FIG. 3 is an exploded view ofthe downstream side of a multi-plate extrusion die for use in apreferred embodiment of the inventive method and with a preferredembodiment of the inventive extrusion line.

FIGS. 2 and 3 illustrate a multi-plate die assembly 22 shown in explodedform consisting of individual die plates 36, 38, 40, 42, 44 and 46, formanufacturing an embodiment of the inventive heat build-up resistantextrudate with a dark-colored capstock. The manner of use of such diesis well known to those of ordinary skill in the thermoplastic extrusionart and is well described in U.S. patent application Ser. No. 09/452,906, entitled “Wood Fiber Polymer Composite Extrusion and Method”assigned to the assignee of the present invention. Disclosure of thatapplication is incorporated herein by reference. Nevertheless, it issufficient to state that the multi-plate die assembly 22 shown in FIGS.2 and 3 is intended for use with a plurality of conventional extruders,such as conventional twin screw extruders, each of which includes amixer or hopper for accepting a thermoplastic feed stock that may or maynot include a filler such as wood flour, a conduit for connecting thehopper with a preheater for controlling the temperature of an admixtureof the feed stock in the hopper, and optionally an inlet for introducingfoaming agents in the case of a foamed component. The multi-screwchamber of each extruder is connected to an appropriate input on the dieassembly plates shown in FIGS. 2 and 3 for producing an embodiment ofthe heat build-up resistant extrudate with a dark-colored capstock shownin FIG. 4.

As best seen in FIGS. 2 and 3, one of the hereinabove describedextruders (not shown) is fluidly connected to an introductory plate 36for introduction of a foamed primary extrudate through the multi-platedie assembly 22. FIGS. 2, 3 and 4 show a foamed primary extrudate butthe invention may also be practiced with a hollow, thin-walled PVC resinor a hollow, thin-walled thermoplastic and wood flour composite. Theembodiment shown in FIGS. 2, 3 and 4 contains a primary extrudate offoamed thermoplastic and preferably a foamed thermoplastic and woodcomposite material. Introductory plate 36 is fluidly connected to atransfer plate 38 which is fluidly connected to substrate capstockingplate 40, mandrel plate 42 and dark-colored capstocking plate 44 andthen to exit plate 46. A substrate capstocking extruder is connected tosubstrate capstocking port 48 of capstocking plate 40 to provide an IRreflective substrate layer on the primary extrudate. A dark-coloredcapstocking extruder is connected to dark-colored capstocking port 50 ofcapstocking plate 40 to provide an IR reflective substrate layer on theprimary extrudate. The mandrel plate 42 that supports a mandrel by meansof a plurality of longitudinally elongated fins within a primary conduitthat runs from primary aperture 52 connected to the primary extruderthrough to the exit aperture 54 which is substantially the desired shapethe final profile. The profile would leave exit aperture 54 insubstantially the final shape of the profile and enter calibrator 26.Visible in FIG. 3 is dark colored capstocking die 44 is fluidlyconnected to dark colored capstock port 50 and which applies the darkcolored capstock over the substrate capstock.

The flow of the primary extrudate and the capstocking material withinthe capstocking conduits 48 and 50 can be readily seen in FIG. 4. FIG. 4is a representation of the flow of the primary extrudate and thecapstocking materials through the multi-plate die assembly 22 which isshown in exploded form in FIGS. 2 and 3. The flow of the primaryextrudate is shown at reference numeral 152 and shows the flow of theprimary extrudate that flows in from the primary extruder into primaryaperture 52 shown in FIG. 2 and out of exit aperture 54 shown in FIG. 3.The substrate capstock flow 148 shows the flow of the NIR reflectivesubstrate that flows from the substrate capstock extruder into substratecapstocking conduit 48 shown in FIGS. 2 and 3 to coat the primaryextrudate. The dark-colored capstock flow 150 is shown as it flowsthrough the multi-plate extrusion die 22 through dark-coloredcapstocking conduit 50 visible in FIG. 2 to coat the NIR reflectivesubstrate capstock.

1. A heat build-up resistant extrudate with a dark-colored capstock,comprising: an IR reflective substrate portion formed of a firstthermoplastic resin that is substantially reflective of solar infraredradiation, a dark-colored capstock portion that is formed of a secondthermoplastic resin that is significantly transmissive of solar infraredradiation and that covers at least a portion of the reflectivesubstrate, and wherein the extrudate exhibits a predicted horizontalheat build-up under ASTM D4803 of less than about 58° Fahrenheit.
 2. Theextrudate with a dark-colored capstock of claim 1, wherein, thedark-colored capstock portion is less than about 30 thousandths of aninch thick, and the first thermoplastic resin contains greater thanabout 8 parts TiO₂ per hundred parts base resin.
 3. The extrudate with adark-colored capstock of claim 2, wherein the dark-colored capstock isless than about 20 thousandths of an inch thick.
 4. The extrudate with adark-colored capstock of claim 2, wherein the dark-colored capstock isless than about 10 thousandths of an inch thick and the firstthermoplastic resin contains between 8 and 11 parts TiO₂ per hundredbase resin.
 5. The extrudate with a dark-colored capstock of claim 2,wherein the dark-colored capstock is between about 4 thousandths andabout 8 thousandths of an inch thick and the first thermoplastic resincontains between 8 and 11 parts TiO₂ per hundred base resin.
 6. Theextrudate with a dark-colored capstock of claim 1, further comprising abase portion formed of a third thermoplastic resin, wherein, the IRreflective substrate portion covers at least part of the surface of thebase portion, and the dark-colored capstock portion covers at least partof the surface of the IR reflective substrate portion.
 7. The extrudatewith a dark-colored capstock of claim 6, wherein the third thermoplasticresin is a rigid, solid thermoplastic.
 8. The extrudate with adark-colored capstock of claim 6, wherein the third thermoplastic resinis a rigid, foamed thermoplastic resin.
 9. The extrudate with adark-colored capstock of claim 6, wherein the base portion is formed ofa rigid, foamed thermoplastic resin and wood flour composite.
 10. Theextrudate with a dark-colored capstock of claim 6, wherein the baseportion is formed of a rigid, foamed thermoplastic resin and mineralfiller composite.
 11. A heat build-up resistant extrudate with adark-colored capstock, comprising: an IR reflective substrate portionformed of a first thermoplastic resin containing between about 8 and 11parts TiO₂ per hundred resin that is substantially reflective of solarinfrared radiation, a dark-colored capstock portion between about 4thousandths and about 8 thousandths of an inch thick that is formed of asecond thermoplastic resin that is significantly transmissive of solarinfrared radiation and that covers at least a portion of the reflectivesubstrate, wherein the extrudate exhibits a predicted horizontal heatbuild-up under ASTM D4803 of less than about 52° Fahrenheit.
 12. Theextrudate with a dark-colored capstock of claim 11, further comprising abase portion formed of a third thermoplastic resin, wherein, the IRreflective substrate portion covers at least part of the surface of thebase portion, and the dark-colored capstock portion covers at least partof the surface of the IR reflective substrate portion.
 13. The extrudatewith a dark-colored capstock of claim 11, wherein the thirdthermoplastic resin is a rigid, solid thermoplastic.
 14. The extrudatewith a dark-colored capstock of claim 11, wherein the thirdthermoplastic resin is a rigid, foamed thermoplastic resin.
 15. Theextrudate with a dark-colored capstock of claim 11, wherein the baseportion is formed of a rigid, foamed thermoplastic resin and wood flourcomposite.
 20. A method of producing a low heat build-up extrudate witha dark-colored capstock, comprising: feeding an IR reflective substrateformed of a first thermoplastic resin that is substantially reflectiveof solar infrared radiation into a first extruder, feeding adark-colored capstock that is formed of a second thermoplastic resinthat is significantly transmissive of solar infrared radiation into asecond extruder, outputting the first and second extruders to anextrusion die that forms the extrudate into a predetermined shape wherethe dark-colored capstock is less than 30 thousandths of an inch thickand covers at least a portion of the IR reflective substrate.
 21. Themethod of claim 20 wherein the first thermoplastic resin containsgreater than about 8 parts TiO₂ per hundred resin.
 22. The method ofclaim 21, wherein the extrusion die forms the dark-colored capstockportion into a layer less than about 20 thousandths of an inch thick.23. The method of claim 21, wherein the extrusion die forms thedark-colored capstock portion into a layer less than about 10thousandths of an inch thick and the first thermoplastic resin containsbetween about 8 and 11 parts TiO₂ per hundred resin.
 24. The method ofclaim 21, wherein the extrusion die forms the dark-colored capstockportion into a layer less than about 8 thousandths of an inch thick andthe first thermoplastic resin contains between about 8 and 11 parts TiO₂per hundred resin.
 25. The method of claim 21, wherein the extrusion dieforms the dark-colored capstock portion into a layer between 4 and 8thousandths of an inch thick and the first thermoplastic resin containsbetween about 8 and 11 parts TiO₂ per hundred resin.
 26. The method ofclaim 21, further comprising: operatively coupling a calibrator to thedownstream end of the extrusion die, and utilizing means forheat-treating the dark-colored capstock portions of the extrudate. 27.The method of claim 26, wherein the means for heat-treating comprisesLeister heaters.
 28. The method of claim 26, wherein the means forheat-treating comprise; a heating tube having upstream and downstreamend and which surrounds the extrudate, and at least one leister heaterdirected so that it blows hot air into at least one end of the heatingtube such that it heats the surface of the extrudate.
 29. The method ofclaim 28, wherein the surface temperature of the extrudate at thedownstream end of the heating tube exceeds a temperature of 115° F. 30.The method of claim 28, wherein the surface temperature of the extrudateat the downstream end of the heating tube exceeds a temperature of 145°F.
 31. The method of claim 25, further comprising: operatively couplinga calibrator to the downstream end of the extrusion die, and operativelycoupling a heating tube having upstream and downstream end and whichsurrounds the extrudate, and includes at least one Leister heaterdirected so that it blows hot air into at least one end of the heatingtube such that it heats the surface of the extrudate such that thesurface temperature of the extrudate at the downstream end of theheating tube exceeds a temperature of 145° F.
 32. The method of claim20, further comprising the feeding a third thermoplastic resin into athird extruder, outputting the third extruder to the extrusion die thatforms the extrudate into a predetermined shape including a base portionformed of a third thermoplastic resin, wherein, the IR reflectivesubstrate portion covers at least part of the surface of the baseportion, and the dark-colored capstock portion covers at least part ofthe surface of the IR reflective substrate portion.
 33. The method ofclaim 32, wherein the third thermoplastic resin is a rigid, solidthermoplastic.
 34. The method of claim 32, wherein the thirdthermoplastic resin is a rigid, foamed thermoplastic resin.
 35. Themethod of claim 32, wherein the base portion is formed of a rigid,foamed thermoplastic resin and wood flour composite.
 36. The method ofclaim 32, wherein the base portion is formed of a rigid, foamedthermoplastic resin and mineral filler composite.
 40. An extrusion linefor the production of a low heat build-up extrudate with a dark-coloredcapstock, comprising: a first extruder for extruding a firstthermoplastic resin that is substantially reflective of solar infraredradiation, a second extruder for extruding a second thermoplastic resinthat is significantly transmissive of solar infrared radiation, anextrusion die operatively coupled to the outputs of the first and secondextruders wherein the extrusion die has upstream and downstream ends andforms the extrudate into a final extrudate of a predetermined profile atthe downstream end that exhibits a predicted horizontal heat build-upunder ASTM D4803 of less than about 58° Fahrenheit and wherein theextrudate comprises: an IR reflective substrate portion that covers atleast a portion of the extrudate and that is formed of the firstthermoplastic resin, and a dark-colored capstock portion that is formedof the second thermoplastic resin that covers at least a portion of thereflective substrate.
 41. The extrusion line of claim 40, wherein thefirst thermoplastic portion contains greater than about 8 parts TiO₂ perhundred resin and the dark-colored capstock portion is less than about30 thousandths of an inch thick.
 42. The extrusion line of claim 41,wherein the dark-colored capstock portion is less than about 20thousandths of an inch thick.
 43. The extrusion line of claim 41,wherein the dark-colored capstock portion is less than about 10thousandths of an inch thick.
 44. The extrusion line of claim 41,wherein the dark-colored capstock portion is less than about 8thousandths of an inch thick.
 45. The extrusion line of claim 41,wherein the dark-colored capstock portion is between 4 and 8 thousandthsof an inch thick.
 46. The extrusion line of claim 41, furthercomprising: a calibrator operatively coupled to the downstream end ofthe extrusion die, and means for heat treating the dark-colored capstockportion of the extrudate.
 47. The extrusion line of claim 46, whereinthe means for heat-treating comprises Leister heaters.
 48. The extrusionline of claim 46, wherein the means for heat-treating comprise; aheating tube having upstream and downstream end and which surrounds theextrudate, and at least one Leister heater directed so that it blows hotair into at least one end of the heating tube such that it heats thesurface of the extrudate.
 49. The extrusion line of claim 48, whereinthe surface temperature of the extrudate at the downstream end of theheating tube exceeds a temperature of 115° F.
 50. The extrusion line ofclaim 48, wherein the surface temperature of the extrudate at thedownstream end of the heating tube exceeds a temperature of 145° F. 51.The extrusion line of claim 40, further comprising, a third extruder forextruding a third thermoplastic resin wherein, the extrusion die isoperatively coupled to the output of the third extruder, the extrusiondie forms the extrudate into a final extrudate of a predeterminedprofile that includes a base portion formed of the third thermoplasticresin, and the IR reflective substrate portion covers at least part of asurface of the base portion, and the dark-colored capstock portioncovers at least part of a surface of the IR reflective substrateportion.
 52. The extrusion line of claim 51, wherein the thirdthermoplastic resin is a is a rigid, solid thermoplastic.
 53. Theextrusion line of claim 51, wherein the third thermoplastic resin is arigid, foamed thermoplastic resin.
 54. The extrusion line of claim 51,wherein the base portion is formed of a rigid, foamed thermoplasticresin and wood flour composite.
 55. The extrusion line of claim 51,wherein the base portion is formed of a rigid, foamed thermoplasticresin and mineral filler composite.